Magnetic-bubble memory device

ABSTRACT

A magnetic-bubble memory device having a bubble propagation track, defined by patterns of magnetically soft material, along which magnetic bubbles propagate in response to an in-plane rotating magnetic drive field. The bubble propagation track has a first track and a second track interconnected by a turn and defined by known hook-shaped wide-gap patterns or by modified wide-gap patterns. The turn includes a crooked bar-shaped pattern. An end portion of the last pattern of the first track is positioned opposite the inner edge of the crooked bar-shaped pattern, and an end portion of the crooked bar-shaped pattern is positioned adjacent to the first pattern of the second track. Such a bubble propagation track makes it possible to realize a 4 μm period, 4 Mb bubble memory.

BACKGROUND OF THE INVENTION

This application is related to two U.S. applications having Ser. No.505,978 filed June 20, 1983 and now U.S. Pat. No. 4,561,069 and Ser. No.513,610 filed July 14, 1983, and now U.S. Pat. No. 4,486,858 which areassigned to the Assignee of the present application.

1. Field of the Invention

The present invention relates to a magnetic-bubble memory device(hereinafter referred to as a bubble memory) and more particularly to abubble propagation track defined by elements or patterns of magneticallysoft material.

2. Description of the Prior Art

There are various known types of bubble memories, the most common onebeing an in-plane field access type of bubble memory which includes athin layer of magnetic material in which magnetic bubbles can bepropagated along propagation tracks in response to a magnetic drivefield rotating or reorienting cyclically in the plane of the magneticmaterial layer. An in-plane field access type of bubble memory in whichthe bit period is 8 micrometers (μm) and the capacity is 1 megabit (Mb)has been realized, and a 4 μm period, 4 Mb bubble memory is now beingdeveloped.

There are two well-known types of propagation tracks, one being definedby elements or patterns of magnetically soft material such as permalloyand commonly called a "permalloy propagation track" and the other beingdefined by an ion-implanted pattern and commonly called an"ion-implanted propagation track". A 4 μm period ion-implanted track canbe easily fabricated and is a very effective means for realizing a 4 μmperiod, 4 Mb bubble memory. However, superior-performance function gatesfor a 4 Mb bubble memory having a 4 μm period ion-implanted track,particularly block-replicate gates for major-minor loop-organized bubblememories, are still in the process of development.

Superior-performance function gates for a bubble memory with a permalloytrack have already been realized. However, in realizing a 4 μm periodpermalloy track, there is a gap problem. There are known gap-tolerantpermalloy propagation patterns, such as half-disk and asymmetric chevronpatterns. However, an allowable gap for a gap-tolerant pattern is, atthe most, one eighth of the period. Therefore, in a 4 μm periodpermalloy track defined by gap-tolerant patterns, the gaps should have awidth of 0.5 μm or less, which cannot be achieved by present-dayphotolithographic resolution.

New permalloy propagation patterns, called wide-gap patterns, have beenreported by A. H. Bobeck et al (EA-1, 3M conference, Atlanta, 1981). Ina wide-gap track defined by wide-gap patterns (explained in detail withreference to the accompanying drawings), superior bubble propagationperformance can be obtained with gaps one fourth of the period.Therefore, a wide-gap pattern is a very promising means for realizing a4 μm period using a 1 μm gap permalloy bubble propagation track whichcan be fabricated by present-day photolithography, thus realizing a 4 μmperiod, 4 Mb bubble memory.

In the design of bubble propagation tracks, 90° and 180° turns areimportant. In particular, for a folded a doubled-back minor loop in amajor-minor loop-organized bubble memory, 180° turns are indispensable.Several turn designs for the wide-gap permalloy propagation trackmentioned above have been reported by A. H. Bobeck et al. However, asexplained below, poor propagation performance is observed for thereported wide-gap track turns.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a wide-gap permalloybubble propagation track of a magnetic-bubble memory device in which thepropagation performance at a turn is superior.

Another object of the present invention is to provide a 4 μm period, 4Mb bubble memory having a wide-gap permalloy propagation track.

According to the present invention, there is provided a magnetic-bubblememory device which includes a magnetic layer in which magnetic bubblescan be moved and bubble propagation tracks along which the bubbles inthe magnetic layer can be propagated in response to a magnetic drivefield rotating in the plane of the magnetic layer. The propagationtracks include at least one loop which has a first track and a secondtrack extending in different bubble propagation directions and a turninterconnecting the first track and the second track. The first trackand the second track are defined by a plurality of hook-shapedpropagation patterns of magnetically soft material. The patterns have afirst end portion and a second end portion and are arranged in thedirection of bubble propagation so that the second end portion of apreceding pattern is not parallel to the first end portion of thesucceeding pattern. The second end portion of the preceding portion isseparated from the first end portion of the succeeding patern and islocated opposite the outer edge of the succeeding pattern. The turnincludes a crooked bar-shaped pattern of magnetically soft material. Thesecond last portion of the end pattern of the first track is positionedopposite the inner edge of the crooked bar-shaped pattern, with a gaptherebetween. An end portion of the crooked bar-shaped pattern islocated adjacent to the first pattern of the second track, with a gaptherebetween. The bubbles propagate from the last pattern of the firsttrack, via the crooked bar-shaped pattern, to the first pattern of thesecond track.

In an embodiment of the present invention, the turn is a 180° turn whichalso includes an auxiliary pattern disposed in a region adjacent to theouter edge of the crooked bar-shaped pattern. The auxiliary pattern hasan end portion disposed adjacent to the end of the crooked bar-shapedpattern and to the first pattern of the second track.

The present invention is now described in detail based on the preferredembodiments and in contrast with the prior art, with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially broken perspective view of a conventionalmagnetic-bubble memory device illustrating the general constructionthereof;

FIG. 2 is a diagrammatical perspective view of part of a conventionalmagnetic-bubble memory chip;

FIGS. 3, 4, and 5 illustrate various conventional permalloy bubblepropagation tracks;

FIGS. 6 and 7 illustrate 8 μm period, 2 μm gap propagation tracksdefined by known wide-gap patterns and conventional half-disk patterns,respectively;

FIG. 8 is a graph showing the propagation characteristics of the tracksillustrated in FIGS. 6 and 7;

FIGS. 9 and 10 illustrate the magnetic characteristics of a wide-gaptrack;

FIG. 11 illustrates the magnetic characteristics of a conventionalpermalloy track;

FIGS. 12, 13, and 14 illustrate various 4 μm period wide-gap tracksdesigned by the inventors of the present invention based on knownwide-gap patterns;

FIG. 15 is a graph showing the propagation characteristics of the tracksillustrated in FIGS. 13 and 14;

FIG. 16 illustrates a 90° turn of a known wide-gap track;

FIG. 17 illustrates an embodiment of the 90° turn of the wide-gap trackaccording to the present invention;

FIG. 18 is a graph showing the propagation characteristics of the tracksillustrated in FIGS. 16 and 17;

FIG. 19 illustrates another embodiment of the 90° turn of the wide-gaptrack according to the present invention;

FIG. 20 illustrates an embodiment of the 180° turn of the wide-gap trackaccording to the present invention;

FIG. 21 is a graph showing the propagation characteristics of the trackillustrated in FIG. 20;

FIGS. 22, 23, 24, and 25 illustrate embodiments of the 180° turn of thewide-gap track according to the present invention;

FIGS. 26 and 27 are graphs showing the propagation characteristics ofthe tracks illustrated in FIGS. 24 and 25, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First, the prior art is described with reference to FIGS. 1 through 11.In FIG. 1, the bubble memory basically comprises a memory chip 1, twocoils 2 and 3 disposed perpendicular to each other for generating anin-plane rotating magnetic field which drives the magnetic bubbles inthe chip, permanent magnets 4 and 5 for generating a bias magnetic fieldwhich maintains the bubbles, and a shield case 6 (illustrated by thephantom line).

In FIG. 2, the memory chip 1 comprises a substrate 1a of, for example,gadolinium-gallium-garnet on which a layer 1b of magnetic material, suchas magnetic garnet, is formed. On the magnetic layer 1b, bubblepropagation tracks PT, defined by bubble propagation patterns ofmagnetically soft material such as permalloy, are formed. The track PTillustrated in FIG. 2 is defined by well-known T- and bar-shapedpatterns.

FIGS. 3, 4, and 5 illustrate various tracks defined by well-knownchevron, half-disk, and asymmetric chevron patterns, respectively. Thehalf-disk and asymmetric chevron patterns are gap-tolerant patterns.

FIG. 6 illustrates an 8 μm period, 2 μm gap wide-gap track defined byone of several kinds of wide-gap patterns reported by A. H. Bobeck etal. The wide-gap pattern, designated by reference numeral 7 (7'), is ahook-shaped or clubfoot-shaped pattern and has a first end portion (aleg) 7a (7a') ad a second end portion (an arm) 7b (7b'). The wide-gaptrack is defined by the hook-shaped patterns 7 (7') which are arrangedin the bubble propagation direction P in such a manner that the arm 7bof the preceding pattern 7 is not parallel to the leg 7a' of thesucceeding pattern 7' and is positioned back from the leg 7a' withrespect to the propagation direction P and opposite the outer edge ofthe succeeding pattern 7', with a gap G therebetween.

FIG. 7 illustrates an 8 μm period, 2 μm gap track defined byconventional half-disk patterns. The adjacent end portions of thehalf-disk patterns are parallel to each other and are on the same levelat the ends thereof with respect to the propagation direction P.

The propagation characteristics of the wide-gap track and the half-disktrack described above are as illustrated in FIG. 8 by the curves L₁ andL₂, respectively, under the conditions of a bubble diameter of 1.9 μmand a drive frequency of 125 kHz. As can be seen, a large bias marginand a required low drive field are obtained in the wide-gap track whilea poor bias margin is obtained in the half-disk track.

The large gap tolerance of the wide-gap track mentioned above isexplained with reference to FIGS. 9, 10, and 11. FIG. 9 illustrates themagnetic potential well depths of the 8 μm period, 2 μm gap wide-gaptrack illustrated in FIG. 6, which depths are measured by observing thereal bubble motion in a quasi-static operation. The curve CF showsbubble collapse fields at each phase of a 58 Oe rotating drive field.The collapse field at point B of the pattern, as is shown in the figure,gradually decreases as the drive field is rotated to 337.5° while thecollapse field at point C of the next pattern has already become higherthan the free-bubble collapse field (FBC) at 315° and graduallyincreases with further drive field rotation. After a phase of 337.5°,the collapse field at point C becomes much higher than that at point B,and the collapse field at point B assumes the same value as that of thefree bubble, which means that point B becomes magnetically neutral.Consequently, a sufficient potential gradient to propagate a bubbleacross the gap can be supplied by repulsive magnetic poles at point A, aneutral pole at point B, and attractive poles at point C.

The superior gap tolerance of the wide-gap track is explained withreference to FIGS. 10 and 11, which illustrate the potential gradientacross the pattern gap for the wide-gap track and the half-disk track,respectively. In the conventional half-disk track, deep and widepotential wells around the gap are deformed, presumably by a potentialbarrier created by widening the gap, as is shown by the broken line inFIG. 11. This potential barrier would prevent most bubbles fromstretching and propagating across the gap; only large-diameter bubbles,that is, bubbles of a low bias-field range, could get across it.However, in the wide-gap track, the above-mentioned magnetic poleformation is supposed to yield a smooth potential gradient when the gapis increased, as is shown in FIG. 10. Therefore, it is assumed that adesign objective for a 4 μm period wide-gap track is to make thepotential gradient between the elements as steep and smooth as possibleby utilizing attractive, neutral, and repulsive magnetic poles. Byfollowing this design rule, many variations in the 4 μm period wide-gaptrack have been constructed and tested.

FIGS. 12-14, illustrate 4 μm period wide-gap tracks. FIG. 12 illustratesa 4 μm period wide-gap track scaled down from the known 8 μm periodwide-gap track shown in FIG. 6. FIGS. 13 and 14 illustrate 4 μm periodwide-gap tracks defined by modified wide-gap patterns designed by theinventors of the present invention. In the pattern 8 illustrated in FIG.13, the leg 8a is longer and the arm 8b is slightly longer than the legand arm of the pattern 7A illustrated in FIG. 12. The second end portion(arm) 8b of a preceeding pattern is positioned opposite the outer edge8c of the succeeding pattern. In the pattern 9 illustrated in FIG. 14,the leg 9a is wider and the arm including trapezoidal extension 9b isslightly longer than the leg and arm of the pattern 8 illustrated inFIG. 13. The propagation characteristics of the tracks illustrated inFIGS. 13 and 14 are illustrated in FIG. 15 by the curves L₃ and L₄,respectively, under the conditions of a bubble diameter of 1.3 μm and adrive frequency of 100 kHz. These characteristics are superior to thoseof the track illustrated in FIG. 12.

FIG. 16 illustrates a 90° turn of a 8 μm period wide-gap permalloy trackreported by A. H. Bobeck et al. In the figure, reference numerals 10 and11 designate first and second straight tracks for bubble propagation inthe directions X and Y, respectively. The tracks 10 and 11 are the sameas those illustrated in FIG. 6. A turn 12 which interconnects the firstand second tracks 10 and 11 includes a hook-shaped permalloy pattern 15,which has the same configuration as the propagation patterns of thetracks 10 and 11. The pattern 15 has an end portion (an arm) 15apositioned adjacent to the end portions (arm and leg) 13a and 14a of thepatterns 13 and 14 at the end of tracks 10 and 11, respectively. In thisprior art turn, however, a steep and smooth magnetic potential gradientbetween the patterns 13 and 15 and between the patterns 15 and 14 cannotbe obtained, and, accordingly, the propagation characteristics are poor,as is illustrated in FIG. 18 by the curve L₅.

FIG. 17 illustrates an embodiment of the 90° turn of the 8 μm periodwide-gap permalloy propagation track according to the present invention.In the figure, reference numerals 20 and 21 designate first and secondtracks which are substantially the same as the tracks 10 and 11,respectively, illustrated in FIG. 16. A turn 22 interconnecting thetracks 20 and 21 includes a crooked bar-shaped permalloy pattern 25disposed between the terminal patterns of the first and second tracks 20and 21, i.e., the last pattern 23 of the first track 20 and the firstpattern 24 of the second track 21. The arm 23a of the end pattern 23 ispositioned opposite the inner edge 25a of the pattern 25, with a gap Gtherebetween. The exit end portion 25b of the pattern 25 is positionedadjacent to the first end portion (leg) 24a of the first pattern 24,with a gap therebetween. It should be noted that it is desirable thatthe arm 23a of the pattern 23 is substantially perpendicular to theinner edge 25a of the pattern 25.

Bubble propagation in the track illustrated in FIG. 17 will now bedescribed. In response to the rotation of the drive field H_(R), abubble moves along the first track 20 in the direction X to the lastpattern 23 and is at the position "1" at phase t₁ of the drive fieldH_(R). The successive rotation of the drive field H_(R) causes thebubble to move successively into the position "2" of the arm 23a of thepattern 23 between phases t₁ and t₂, into the position "3" of the endportion 25b of the pattern 25 between phases t₂ and t₃, and into theposition "4" of the leg 24a of the first pattern 24 of the second track21 between phases t₃ and t₄. Further successive rotation of the drivefield H_(R) causes the bubble to move, via the position "5", along thesecond track 21 in the direction Y.

In the track of the present invention described above, a steep andsmooth magnetic potential gradient between the patterns 23 ad 25 andbetween the patterns 25 and 24 can be realized, and, accordingly,superior propagation characteristics as illustrated in FIG. 18 by thecurve L₆ can be obtained.

FIG. 19 illustrates another embodiment of the 90° turn of the 8 μmperiod wide-gap track according to the present invention. Thisembodiment is basically the same as that illustrated in FIG. 17 exceptthat the pattern 25A in the turn 22A has a different configuration thandoes the pattern 25 in the turn 22 of FIG. 17. The propagationcharacteristics of this embodiment are equal to or superior to those ofthe embodiment illustrated in FIG. 17.

FIG. 20 illustrates an embodiment of the 180° turn of the 8 μm periodwide-gap permalloy track according to the present invention. In FIG. 20,reference numerals 30 and 31 designate first and second tracks which arethe same as the tracks 20 and 21, respectively, illustrated in FIG. 17except that bubble propagation is in the directions X and X'. A turn 32interconnecting the tracks 30 and 31 includes a first, or main, crookedbar-shaped permalloy pattern 35 and a second, or auxiliary, crookedbar-shaped permalloy pattern 36. The arm 33a of the last pattern 33 ofthe first track 30 is positioned opposite the inner edge 35a of the maincrooked bar-shaped pattern 35, with a gap therebetween. The end portion35b of the main pattern 35 is adjacent to the leg 34a of the firstpattern 34 of the second track 31. The auxiliary pattern 36 is disposedin a region adjacent to the outer edge 35c of the main pattern 35 so asto extend substantially parallel to the latter and has an exit endportion 36 a adjacent to the end portion 35b of the main pattern 35 andto the first pattern 34 of the second track 31.

In the track described above, a bubble propagates along the first track30 in the direction X and, from the pattern 33, via the pattern 35, tothe pattern 34, and further along the second track 31 in the directionX'. A steep and smooth magnetic potential gradient between the patterns33 and 35 and the patterns 35 and 34 is realized, and, accordingly, thesuperior propagation characteristics illustrated in FIG. 21 can beobtained. It should be noted that the auxiliary pattern 36 contributesto realization of the steep and smooth magnetic potential gradientbetween the patterns 35 and 34.

FIGS. 22 and 23 illustrate further embodiments of the 180° turn of the 8μm period wide-gap permalloy propagation track according to the presentinvention. These embodiments are basically the same as the embodimentillustrated in FIG. 20 except for the configurations of the mainpatterns 35A and 35B and the auxiliary patterns 36A and 36B of the turns32A and 32B in FIGS. 22 and 23, respectively. The propagationcharacteristics of these tracks are equal to or superior to those of theembodiment illustrated in FIG. 20.

FIGS. 24 and 25 illustrate embodiments of the 180° turn of the 4 μmperiod wide-gap permalloy track according to the present invention. InFIG. 24, reference numerals 40 and 41 designate first and secondstraight tracks for bubble propagation in the directions X and X',respectively. The tracks 40 and 41 are defined by propagation patternssimilar to the modified and improved wide-gap pattern illustrated inFIG. 13. A turn 42 includes a main crooked bar-shaped pattern 45 and anauxiliary crooked bar-shaped pattern 46. The positional relationshipbetween the first and second terminal patterns 43 and 44 of the tracks40 and 41, respectively, and the patterns 45 and 46 of the turn 42 isthe same as that in the embodiment illustrated in FIG. 20, only thewidth of the gaps and the size and shape of the patterns are different.For example, the first terminal pattern 43 has a first end portion 43a,a mid-portion 43b and a second end portion 43c with a tip 43d and acenter line. Similarly, the second terminal pattern 44 includes a firstend portion 44a connected via a curve 44b to a mid-portion 44c and asecond end portion 44d. The pattern 44 is thus a preceeding pattern forsucceeding pattern 44'. The main crooked bar-shaped pattern 45 has firstand second arms 45a and 45b with tips 45c and 45d.

The embodiment illustrated in FIG. 25 is basically the same as theembodiment illustrated in FIG. 24 except for the configuration of thepatterns in the tracks 40A and 41A and the turn 42A. In particular, theauxiliary pattern 46A of the turn 42A has an end portion 47 which has aconfiguration considerably different from the end portion of theauxiliary pattern 46 illustrated in FIG. 24. The auxiliary pattern 46Aalso includes a first arm 46a, mid-portion 46b and tip 47a on the secondarm 47.

The propagation characteristics of the tracks illustrated in FIGS. 24and 25 are illustrated in FIGS. 26 and 27, respectively, assuming that a5 Oe in-plane holding field H₁ or H₂ is applied to the tracks asillustrated in FIGS. 24 and 25. The curves L₇ and L₉ represent the casesin which the field H₁ is applied, and the curves L₈ and L₁₀ representthe cases in which the field H₂ is applied.

As is obvious from the foregoing description, the present inventionmakes it possible to realize a 4 μm period permalloy bubble propagationtrack in which, particularly in the turn, superior propagationcharacteristics are obtained, and, accordingly, a 4 μm period, 4 Mbbubble memory can be obtained.

I claim:
 1. A magnetic-bubble memory device in which magnetic bubblesare driven by a magnetic drive field, comprising:a magnetic layer inwhich the magnetic bubbles can be propagated; and a bubble propagationpath along which the bubbles in said magnetic layer can be propagated inresponse to the magnetic drive field rotating in the plane of saidmagnetic layer, said bubble propagation path comprising:first and secondtracks, extending in different bubble propagation directions, comprisinghook-shaped propagation patterns of magnetically soft material,including first and last patterns in each of said first and secondtracks, each of the hook-shaped propagation patterns having a first endportion, a second end portion and an outer edge, said hook-shapedpropagation patterns arranged in the bubble propagation directions withthe second end portion of a preceding pattern not parallel to the firstend portion of the succeeding pattern and the second end portion of thepreceding pattern disposed opposite and separated from the outer edge ofthe succeeding pattern; and a turn, interconnecting the first and secondtracks, comprising a crooked bar-shaped pattern of magnetically softmaterial having an exit end portion with an inner edge, the second endportion of the last pattern in said first track disposed opposite andseparated from the inner edge of the exit end portion of said crookedbar-shaped pattern, the exit end portion of said crooked bar-shapedpattern disposed adjacent to and separated from the first end portion ofthe first pattern in said second track, whereby the magnetic bubblespropagate from the last pattern in said first track, via said crookedbar-shaped pattern, to the first pattern in said second track.
 2. Amagnetic-bubble memory device according to claim 1, wherein the secondend portion of the last pattern in said first track is substantiallyperpendicular to the inner edge of the exit end portion of said crookedbar-shaped pattern.
 3. A magnetic-bubble memory device according toclaim 1, wherein said turn is a 90° turn.
 4. A magnetic-bubble memorydevice according to claim 1, wherein said turn is a 180° turn.
 5. Amagnetic-bubble memory device according to claim 4, wherein said turnfurther comprises an auxiliary pattern disposed adjacent to andseparated from the outer edge of said crooked bar-shaped pattern, saidauxiliary pattern having an exit end portion disposed between andseparated from the exit end portion of said crooked bar-shaped patternand the first pattern in said second track.
 6. A magnetic-bubble memorydevice according to claim 5, wherein said auxiliary pattern extendssubstantially parallel to said crooked bar-shaped pattern.
 7. Amagnetic-bubble memory device according to claim 1, wherein said bubblepropagation path has a pattern period of approximately 8 μm.
 8. Amagnetic-bubble memory device according to claim 1, wherein said bubblepropagation path has a pattern period of approximately 4 μm.
 9. Amagnetic-bubble memory device according to claim 1, wherein each of thehook-shaped propagation patterns has a U-shape with the first endportion fully extended and the second end portion truncated aftercompletion of the base of the U-shape and the second end portion of eachof the hook-shaped propagation patterns includes a trapezoidal extensiontapering away from the base of the U-shape.
 10. A magnetic-buble memorydevice for magnetic bubbles driven by a magnetic drive field,comprising:a magnetic layer in which the magnetic bubbles can bepropagated; and a bubble propagation track in said magnetic layer, themagnetic bubbles propagating in a bubble propagation direction alongsaid bubble propagation track in response to the magnetic drive fieldrotating in the plane of said magnetic layer, said bubble propagationtrack comprising hook-shaped patterns, each of the hook-shaped patternshaving a first end portion with a first length and a tip, a mid-portionperpendicular to the first end portion, a curve connecting themid-portion and the first end portion and a second end portion having asecond length, the second length being shorter than the first length,the second end portion of a preceding hook-shaped pattern being followedin the bubble propagation direction by the first end portion of asucceeding hook-shaped pattern.
 11. A magnetic-bubble memory deviceaccording to claim 10, wherein the second end portion of the preceedinghook-shaped pattern is disposed opposite the succeeding hook-shapedpattern at the curve connecting the first end portion and themid-portion of the succeeding hook-shaped pattern.
 12. A magnetic-bubblememory device according to claim 10, wherein the hook-shaped patternsare arranged in first and second bubble propagation directions and saidbubble propagation track further comprises a 180° turn comprising:afirst terminal pattern having a mid-portion, a first end portion and asecond end portion having a tip and a first center line, said firstterminal pattern positioned in the first bubble propagation directionwith the first end portion of said first terminal pattern disposedopposite and separated from the second end portion of the precedinghook-shaped pattern arranged in the first bubble propagation direction;a main crooked bar-shaped pattern, having a first arm with a tip alignedin the first bubble propagation direction with the mid-portion of saidfirst terminal pattern and a second arm with a second center linesubstantially perpendicular to the first center line and a tip alignedwith the tips of the first end portion of the hook-shaped patternsarranged in the second bubble propagation direction; an auxiliarycrooked bar-shaped pattern having a first arm substantially parallel tothe first arm of said main crooked bar-shaped pattern, a mid-portionsubstantially parallel to the second arm of the main crooked bar-shapedpattern and a second arm with a tip disposed opposite and separated fromthe curve of the succeeding hook-shaped pattern in the second bubblepropagation direction.
 13. A magnetic-bubble memory device according toclaim 12, wherein the second arm of said auxiliary crooked bar-shapedpattern is perpendicular to the mid-portion of said auxiliary crookedbar-shaped pattern and the tip of the second arm of said auxiliarycrooked bar-shaped pattern is aligned with the second center line.